Rotary machines typically utilize vane motors that are pneumatically powered to cause rotation of the output shaft. As is well known these machines comprise a cylinder, sometimes referred to as a casing and a spindle rotary mounted in a cylinder and eccentrically spaced relative to the center line of the bore of the cylinder, sometimes referred to as a rotor. The cylinder is stationary and through apertures in the cylinder lead pressurized air to impinge on the working face of the reciprocating vanes mounted in slots formed in the spindle to cause the spindle to rotate and then exhaust the spent air through additional holes formed in the cylinder. In surgical pneumatic drills, for example, the spent air is exhausted through the cylinder and is directed toward the aft end thereof to flow into the outer passageway of a coaxial hose that includes an inner passageway that flows the pressurized air into the motor housing which, in turn, is directed to the cylinder for powering the vane motor. The problem that this invention solves is directed to the noise that is generated by the exhaust air that is being returned to the coaxial hose.
This invention solves the noise problem by providing apparatus that includes cris-cross passages that flow the fluid in a judicious manner so that a certain amount of decibels are automatically canceled. Air flow with a pulsating pressure pattern is diverted so that half the flow is directed in one axial passageway and the other half is directed in another passageway. By virtue of flowing a portion the air to flow in separate passageways reduces the amplitude of the pressure. That flow in both passageways are then directed to cross each other. The effect of the flow crossing causes the flow to impinge on the flow from each of the passageways and this impact cancels or nearly cancels the amplitude of the pressure which results in a reduction of decibels and an overall reduction in the noise level. In this invention, one of the embodiments includes an end cap that fits the aft end of the motor of a surgical drill and that has discrete cris cross passages and the other embodiment includes a plug that is inserted into the hose that serves to admit and discharge air and this embodiment includes discrete cris-cross passages to direct the flow of the air in a cris-cross pattern to effectuate the decrease of decibels resulting in an overall reduction of the noise level.